Gretchen had $15,000 to invest (Current Year $, year 0), which she invested for 10 years. During this investment period the market rate of return was 12%. After 10 years her investment was worth $37,063 in current year dollars (year O). What was average inflation that occured during the 10 years investment period? 2.2% 2.4% 3.5% 9.5% 3.8%